Interpretive Summary: Understanding poultry immune system is important in the study of host-pathogen
immunobiology. There is a critical lack of information on the nature of dendritic cells which play
an important role in initiating immune response to pathogens in avian species. In this study, ARS scientists collaborated with researchers at the University of Zaragosa, Spain, to isolate two different types of dendritic cells using antibodies detecting Eimeria specifically. Using this antiserum, they were able to localize antigen-binding cells in intestinal tissue of the of parasite-infected chickens. Detailed ultrastructural studies revealed that follicular dendritic cells are different from interdigitating dendritic cells in their expression of surface markers and their function in antigen presentation. In summary, this is the first paper documenting clear evidence for the existence of different types of dendritic cells in poultry. The results provide enhanced insights on the nature of interactions which are necessary for effective immune response to pathogens during infection process.

Technical Abstract:
An antiserum against Eimeria tenella sporozoites was used to localize and isolate Ag-binding cells in intestinal cecal tonsils of parasite-infected chickens. Based on their tissue localization, ultrastructural features, and expression of surface markers, two subpopulations of cells were isolated, CD45+ interdigitating dendritic cells (IDCs)3 and CD45- follicular dendritic cells (FDCs). IDCs expressed MHC class I, MHC class II, and selectin, induced the proliferation of allogeneic naïve CD4+ T cells, and increased the secretion of IFN-' by autologous T cells. FDCs expressed surface IgG, IgM, ICAM-1, and VCAM-1, stimulated the proliferation of LPS-treated allogeneic B cells, and augmented the secretion of IgG by LPS-treated autologous B cells. Final cell yields were 6 x 105 to 8 x 105 cells per chicken with > 95% purity. In summary, this combination of methods using Abs against E. tenella and chicken CD45 made it possible to obtain a substantial number of highly enriched IDCs and FDCs which are functionally active for the first time. This novel method will facilitate the detailed biochemical and immunological characterizations of avian dendritic cells and enable the investigation of their role in initiating immune response in normal and disease states.